TerraSAR-X and TanDEM-X Formation Acquires First Bi-static Dataset

Digital Elevation Model of Mount Etna created

The German Aerospace Center (DLR) has announced that the TanDEM-X and TerraSAR-X satellite pair have acquired their first image of Earth’s surface, synchronised to the microsecond, while flying over Mount Etna in Italy. The image, taken while the satellites were flying just 350 metres apart, is the first in the world to be made by satellites flying in such a close formation.

The German Aerospace Center (DLR) has announced that the TanDEM-X and TerraSAR-X satellite pair have acquired their first image of Earth’s surface, synchronised to the microsecond, while flying over Mount Etna in Italy. Scientists at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) have used the data to create a three-dimensional digital elevation model with an unprecedented elevation accuracy down to two metres. The image, taken while the satellites were flying just 350 metres apart, is the first in the world to be made by satellites flying in such a close formation.

The image shows Mount Etna on the east coast of Sicily. This three-dimensional view of the volcano was generated from data recorded by TanDEM-X and TerraSAR-X. This was acquired using bistatic radar, where one of the satellites transmits a radar signal to Earth and the two satellites receive the reflection of this signal simultaneously. In this way, a highly accurate three-dimensional terrain model is created on a 12-metre grid. A similar recording technique was used in the Shuttle Radar Topography Mission (SRTM) in February 2000. However, in this case only 60 percent of Earth's surface was imaged, and at a coarser grid spacing of 30 to 90 metres.

Satellite pair captures detail from space

Comparison of the TanDEM-X elevation model with data acquired ten years previously by SRTM demonstrates the improvement in precision; the difference between the elevations measured today and the SRTM elevation data is represented in colour on a TanDEM-X radar image of the area surrounding Mount Etna. In the area of the actual crater especially and along the flanks of the volcano there are differences of up to 30 metres.

Milestone on the way to a 3D elevation model of the Earth

The first images taken in close flying formation form the foundation of the mission objective; from 2011 the two satellites will spend three years systematically measuring the entire surface of Earth multiple times with great precision. The radar satellites can observe the 150 million square kilometres of Earth’s surface around the clock, without interruption from the weather and clouds. The data acquired can be used for mapping the landscape, city planning and navigation, as well as for mission planning in disaster areas. It can also be used for scientific research in glacial, earthquake or volcanic regions.

Public-Private Partnership

The DLR is responsible for the scientific use of the TanDEM-X data, planning and executing the mission, controlling the two satellites and generating the digital elevation model. Astrium built the satellites and contributed to the cost of their development and deployment. As with TerraSAR-X, Infoterra GmbH, a subsidiary of Astrium, is responsible for the commercial marketing of the TanDEM-X data.

The TanDEM-X mission is being operated by the German Aerospace centre (DLR) with funding from the German Federal Ministry for Economics and Technology (Bundesministerium für Wirtschaft und Technologie; BMWi), in the form of a public-private partnership with Astrium GmbH.